Method for fabricating semiconductor structure, and solid precursor delivery system

ABSTRACT

A method for fabricating a semiconductor structure is provided, including: providing a solid precursor having a first average particle size; solving the solid precursor in an organic solvent into an intermediate; recrystallizing the intermediate to form solid granules, wherein the solid granules has a second average particle size larger than the first average particle size; vaporizing the solid granules to form a film-forming gas; and depositing the film-forming gas on a substrate to form a resistance film. A method for modifying a resistance film source in a semiconductor fabrication and a solid precursor delivery system are also provided. The method for fabricating a semiconductor structure in the present disclosure can remove small particles or ultra-small particles from solid precursor, and does not need extra time to dump cracked solid precursor.

BACKGROUND

As the dimension of a semiconductor device is getting less, the gatestructure and the thickness of the gate insulation layer are reducedaccordingly. However, a leakage current occurs when the gate insulationlayer of silicon oxide becomes thinner. To address the current leakage,high-k/metal gate (HK/MG) technology is used in semiconductor structure,adopting high-k material to replace silicon oxide, and metal gate toreplace polysilicon gate accordingly. The HK/MG technology canfacilitate the gate close/open rate and reduce current leaked from gateto body.

For the HK/MG technology, there are layers of films deposited on themetal gate, and good particle source control (i.e., solid sourceprecursor of particle free) is required to avoid pits defect withinmetal gate during the deposition of the films. Any kind of particlesource come from solid source precursor would easily impact performanceof the semiconductor device.

To deposit films on the metal gate, atomic layer deposition (ALD) isused extensively. ALD is a process using precursor materials as a sourceto deposit the required film on a substrate, the precursor can be gas,liquid, or solid, and the precursor is transformed into its gas statefor deposition. For instance, if a solid precursor is used,untransformed small particles from the solid precursor may fall on asemiconductor wafer center during carrier gas delivery and block thesubsequent gate filling process within poly removal metal gate. Smallparticle is a strong blocking particle that would block the gate fillingprocess and cause pits defect after chemical mechanical polishing (CMP),which affects the performance of the semiconductor device.

The above situation can be reduced by thermal caking, which uses heat tofuse particles of the solid precursor to become a cake of precursor in acontainer. However, the cake is still apt to crack and induceultra-small particles during transportation of the container. In orderto remove the ultra-small particles, it takes extra time to dump crackedsolid precursor up to about one fifth of the solid precursor. Therefore,there is a need for a method to avoid the forming of small particles orultra-small particles, and to facilitate the semiconductor fabrication.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are best understood from thefollowing detailed description when read with the accompanying figures.It is emphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a flow chart illustrating a method for fabricating asemiconductor structure.

FIG. 2 is a flow chart illustrating a method for modifying a resistancefilm source in a semiconductor fabrication.

FIG. 3 is a solid precursor delivery system for a semiconductorfabrication in accordance with one embodiment in the present disclosure.

FIG. 4 illustrates changes in particle size of a solid precursor andsolid granules.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Moreover,the formation of a first feature over or on a second feature in thedescription that follows may include embodiments in which the first andsecond features are formed in direct contact, and may also includeembodiments in which additional features may be formed interposing thefirst and second features, such that the first and second features maynot be in direct contact. Various features may be arbitrarily drawn indifferent scales for the sake of simplicity and clarity.

The singular forms “a,” “an” and “the” used herein include pluralreferents unless the context clearly dictates otherwise. Therefore,reference to, for example, a metal gate includes embodiments having twoor more such metal gates, unless the context clearly indicatesotherwise. Reference throughout this specification to “one embodiment”or “an embodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present disclosure. Therefore, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Further, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments. It should be appreciated that the followingfigures are not drawn to scale; rather, these figures are intended forillustration.

Referring to FIG. 1, a method for fabricating a semiconductor structureis illustrated in accordance with various embodiments of the presentdisclosure. In operation 110, a solid precursor having a first averageparticle size is provided. In one embodiment, the first average particlesize is in the range of 300 μm to 500 μm.

In operation 120, the solid precursor is solved in an organic solvent toto form an intermediate.

In operation 130, the intermediate is recrystallized to form solidgranules, and the solid granules have a second average particle sizelarger than the first average particle size. Recrystallizing theintermediate may be performed at a temperature in the range of −30° C.to 10° C. In one embodiment, the second is average particle size is inthe range of 1 mm to 10 mm. In another embodiment, the purity of thesolid source after recrystallization is greater than 99.999%, while thepurity of the solid source is about 99.99% in exiting methods.

Still referring to FIG. 1, in operation 140, the solid granules arevaporized to form a film-forming gas, and in operation 150, thefilm-forming gas is deposited on a substrate to form a resistance film.In one embodiment, the substrate is a semiconductor wafer. In anotherembodiment, the substrate is a metal gate.

Referring to FIG. 2, a method for modifying a resistance film source ina semiconductor fabrication is illustrated in accordance with variousembodiments of the present disclosure. In one embodiment, thesemiconductor fabrication is an atomic layer deposition process, and theatomic layer deposition process may be applied in high-k metal gatetechnology.

In operation 210, a solid precursor is solved in an organic solvent toform an intermediate. In operation 220, the intermediate isrecrystallized to form solid granules, and the recrystallization may beperformed at a temperature in the range of −30° C. to 10° C.

In operation 230, the solid granules are transported to a collectingroom. Then, in operation 240, the solid granules are vaporized to form afilm-forming gas. The solid granules may be vaporized by heating thecollecting room to a temperature above the melting point of the solidgranules.

Still referring to FIG. 2, in operation 250, the film-forming gas isdelivered to a deposition chamber by a carrier gas. In one embodiment,the carrier gas is an inert gas. In another embodiment, the carrier gasis argon.

FIG. 3 is a solid precursor delivery system 300 for a semiconductorfabrication in accordance with one embodiment in the present disclosure.The solid precursor delivery system 300 included a recrystallizingreservoir 310, a gas tank 320, a deposition chamber 330, and acollecting room 340. The recrystallization reservoir 310 includescooling elements 312 around the recrystallization reservoir 310, aprecursor entry port 314, a solvent entry port 316, and a granule exitport 318. A solid precursor and an organic solvent (not shown) areprovided to the recrystallization reservoir 310 through the precursorentry port 314 and the solvent entry port 316 respectively, and thesolid precursor is solved into an intermediate. Then, therecrystallization reservoir 310 is cooled by the cooling elements 312 torecrystallize the intermediate and form solid granules. Afterrecrystallization, the solid granules are transported to the collectingroom 340 through the granule exit port 318.

The solid precursor may be Pentakis-dimethylamino tantalum (PDMAT),tantalum chloride (TaCl₅), tantalum fluoride (TaF₅), hafnium chloride(HfCl₄), niobium fluoride (NbF₅), or molybdenum fluoride (MoF₅), and theorganic solvent may be pentane, hexane, cyclopentane, or cyclohexane.

Still referring to FIG. 3, the collecting room 340 includes heatingelements 342 around the collecting room 340, a granule entry port 344connecting to the granule exit port 318, a gas entry port 346 connectingto the gas tank 320, and a gas exit port 348 connecting to thedeposition chamber 330. After the solid granules were transported to thecollecting room 340 through the granule entry port 344, the collectingroom 340 is heated to a temperature above the melting point of the solidgranules by the heating element 342 to vaporize the solid granules andform a film-forming gas. Then, the carrier gas in the gas tank 320enters the collecting room 340 through the gas entry port 346, and exitsthrough the gas exit port 348 carrying the film-forming gas to deliverthe film-forming gas to the deposition chamber 330. In one embodiment,the gas tank 320 is an inert gas tank. In another embodiment, the gastank 320 is an argon gas tank.

After the film-forming gas was delivered to the deposition chamber 330,the film-forming gas deposits in the deposition chamber 330 to form aresistance film on a substrate. The deposition chamber 330 may be anatomic layer deposition chamber, and the atomic layer deposition chambermay be applied in high-k metal gate technology.

FIG. 4 illustrates changes in particle size of a solid precursor 402 andsolid granules 404 in accordance with various embodiments of the presentdisclosure. Referring to FIG. 3 and FIG. 4, a solid precursor 402 has afirst average particle size, and after recrystallizing in therecrystallization reservoir 310, the solid precursor 402 becomes solidgranules 404 having a second average particle size larger than the firstaverage particle size, which the first average particle size is in therange of 300 μm to 500 μm, and the second average particle size is inthe range of 1 mm to 10 mm. The solid granules 404 keeps stable duringtransportation, and there is no small particles or ultra-small particlesformed. Thus, the gate would not be blocked by particles and there wouldbe no need to take extra time to dump cracked solid precursor, which areadvantages and problems solved of the present disclosure.

It is noteworthy that the transportation mentioned above may betransporting the recrystallization reservoir 310 with solid granules 404inside, transporting the collecting room 340 with solid granules 404inside, or transporting the solid granules 404 from therecrystallization reservoir 310 to the collecting room 340.

The embodiments of the present disclosure discussed above haveadvantages over exiting methods and systems. Because of therecrystallization of the solid precursor prior to deposition, smallparticles or ultra-small particles from solid precursor can be removed,and the purity of the solid source can be improved. The method forfabricating a semiconductor structure in the present disclosure does notneed extra time to dump cracked solid precursor, which saves time andraw materials. It is understood, however, that other embodiments mayhave different advantages, and that no particular advantages is requiredfor all embodiments.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for fabricating a semiconductorstructure, comprising: providing a solid precursor having a firstaverage particle size; solving the solid precursor in an organic solventinto an intermediate; recrystallizing the intermediate to form solidgranules, wherein the solid granules have a second average particle sizelarger than the first average particle size; vaporizing the solidgranules to form a film-forming gas; and depositing the film-forming gason a substrate to form a resistance film.
 2. The method of claim 1,wherein fabricating the semiconductor structure is performed by atomiclayer deposition.
 3. The method of claim 1, wherein the first averageparticle size is in the range of 300 μm to 500 μm.
 4. The method ofclaim 1, wherein recrystallizing the intermediate is performed at atemperature in the range of −30° C. to 10° C.
 5. The method of claim 1,wherein the second average particle size is in the range of 1 mm to 10mm.
 6. The method of claim 1, wherein depositing the film-forming gas isdepositing on a semiconductor wafer.
 7. The method of claim 6, whereindepositing the film-forming gas is depositing on a metal gate.
 8. Amethod for modifying a resistance film source in a semiconductorfabrication, comprising: solving a solid precursor in an organic solventinto an intermediate; recrystallizing the intermediate to form solidgranules; transporting the solid granules to a collecting room;vaporizing the solid granules by to form a film-forming gas; and todelivering the film-forming gas to a deposition chamber by a carriergas.
 9. The method of claim 8, wherein the semiconductor fabrication isan atomic layer deposition process.
 10. The method of claim 9, whereinthe atomic layer deposition process is applied in high-k metal gatetechnology.
 11. The method of claim 8, wherein recrystallizing theintermediate is performed at a temperature in the range of −30° C. to10° C.
 12. The method of claim 8, wherein delivering the film-forminggas is performed by an inert gas.
 13. The method of claim 12, whereindelivering the film-forming gas is performed by argon.
 14. A solidprecursor delivery system for a semiconductor fabrication, comprising: arecrystallization reservoir, comprising: cooling elements around therecrystallization reservoir; a precursor entry port, wherein a solidprecursor enters the recrystallization reservoir through the precursorentry port; a solvent entry port, wherein an organic solvent enters therecrystallization reservoir through the solvent entry port; and agranule exit port; a gas tank; a deposition chamber; and a collectingroom, comprising: heating elements around the collecting room; a granuleentry port connecting to the granule exit port; a gas entry portconnecting to the gas tank; and a gas exit port connecting to thedeposition chamber.
 15. The system of claim 14, wherein the solidprecursor is Pentakis-dimethylamino tantalum (PDMAT), tantalum chloride(TaCl₅), tantalum fluoride (TaF₅), hafnium chloride (HfCl₄), niobiumfluoride (NbF₅), or molybdenum fluoride (MoF₅).
 16. The system of claim14, wherein the organic solvent is pentane, hexane, cyclopentane, orcyclohexane.
 17. The system of claim 14, wherein the gas tank is aninert gas tank.
 18. The system of claim 17, wherein the gas tank is anargon gas tank.
 19. The system of claim 14, wherein the depositionchamber is an atomic layer deposition chamber.
 20. The method of claim19, wherein the atomic layer deposition chamber is applied in high-kmetal gate technology.